Drill holder



June 14, 1960 D. K. APPLEBY DRILL HOLDER Filed June 27, 1957 0 c c R? W.

1 w Z WW m Patented June 14, 1960 nice DRILL HOLDER David K. Appleby,Penn Acres, Del., assignor to Enterprise Machine and DevelopmentCorporation, New Castle, Del., a corporation of Delaware Filed June 27,1957, Ser. No. 668,404

15 Claims. (Cl. 279-16) This invention relates to a holder for smalldiameter drills, and more particularly relates to a holder for mountingand centering micro drills in the rotating holder of a drill press.

The term micro drill is used to designate a small diameter drill, forexample, ranging from approximately ,4 of an inch in diameter down to0.001 of an inch in diameter. These micro drills are, for example,conventionally designated by 0.001 inch diameter sizes. A drill of anysize tends to wobble or rotate eccentrically withinthe rotating holderor chuck of a drill press by virtue of the inherent inaccuraciesincorporated in standard bearings, shafts and holding devices. Thisproblem assumes major proportions in using micro drills where theeccentricity is of an order equal to'and sometimes larger than thediameter of the drill itself. Means must, therefore, be provided forcentering the drill in the rotating holder.

Various floating or self-aligning tool holders have been proposed. Thesedevices, however, usually include amultiplicity of preciselymanufactured and assembled parts. Examples of these prior art devicesare described in US. Letters Patents 2,297,064, 2,432,350, and 2,-778,647.

An object of this invention is to provide a simple and economical devicefor mounting and centering a standard micro drill in a conventionalrotating holder.

In accordance with this invention, a device for mounting and centering amicro drill in a rotating holder includes a shank having a micro drillchuck disposed at one end. A circumferential protuberance is formedadjacent the other end of the shank which is inserted into the rotatingholder. This protuberance provides suflficient area of contact betweenthe shank and the rotating holder to drive the micro drill under load,and it projects outwardly from the rest of the shank a distancesufiicient to permit the device to pivot about it within the rotatingholder to center the drill upon he application of a lateral drillcentering force to the lower end of the device.

Novel features and advantages of this invention will become apparent toone skilled in the art from a reading of the following description inconjunction with the accompanying drawings wherein similar referencecharacters refer to similar parts and in which:

Fig. 1 is a view in elevation of an embodiment of this invention;

Fig. 2 is a plan view of the embodiment shown in Fig. 1;

Fig. 3 is a cross-sectional view in elevation of the embodiment shown inFig. 1;

Fig. 4 is a cross-sectional view taken through Fig. 3 along the line4-4;

Fig. 5 is a cross-sectional view taken through Fig. 3 along the line 55;and

Figs. 6-10 are views in elevation of modifications of the embodimentshown in Fig. 1.

In Figs. 1 and 2 is shown a device 10 for mounting and centering a microdrill 12, for example, a long slender micro drill of the type usuallydescribed as a wire drill, in a rotating holder 14, for example, betweenjaws 16 of a conventional four-jawed chuck 14. Device 10 includes ashank 18 with a micro drill chuck 20 disposed at one end, and acircumferential protuberance 22 disposed at the other end. 1

Figs. 3-5 show details of device 10.v Micro chuck 20, for example, is acollet type chuck including, for example, a three-jawed spring colletassembly 24-disposed within a central bore or recess 26 extendingthrough the lower end 28 of a larger diameter section 25 of shank 18.Section 25 is sufliciently large in diameter to receive collet assemblyshank 30 within it and to provide coupling means, threads 34 forexample, for attaching collet closing ring 32. The diameter ofsection'25 is, forexample, inch to engage standard micro wdrill chucks.Collet type chuck 20 is a conventional type, but it might be replaced byany conceivable device for securely holding a micro drill. The termchuck is, therefore, used herein to designate any and all types of drillholding devices.

Smaller diameter section 27 of shank 18 remote from chuck 20 includes acircumferential protuberance 22. Protuberance 22 is disposed, forexample, approximately at the center of section 27 which tapersgradually down on both sides of protuberance 22 to smaller diameters atend 36 and at neck 38 which joins the larger diameter section 25. Thediameter of protuberance 22 is large enough to be conveniently graspedwithin the jaws 16 of rotating holder 14. It projects outwardly from therest or root of the shank a distance sui'icient to permit the device topivot about it within the .jaws upon the 'application of a lateralcentering force to the lower portion of the device, for example,to asmooth portion of chuck 20. The diameter of protuberance 22 should besomewhat larger than the diameter of the largest micro drill size,namely, approximately somewhat larger. than ,4 inch to providea'convenient and strong configuration. An-efiective protuberance is, forexampleQformed at the center of section 27 which is approximately /2inch long. The diameter at protuberance 22 is, for example,approximately of an inch, and shank section 27 tapers gradually from itto a root diameter at end 36 and neck 38.which is, for example,approximately 4: inch.

Device 10 should be long enough to permit a micro drill held by it tobecome centered even if device 10 wobbles or runs eccentrically at itsprotuberance. An overall length of approximately 1 /2 inches isconvenient and operative.

It is advantageous to make the taper of the smaller diameter section ofthe shank sufiiciently shallow to prevent it from passing between theareas of contact provided by the jaws 16 of rotating holder -14 when thedevice is rocked about protuberance 22. This limits the extent of therocking motion and prevents the chuck from inadvertently passing out ofcontrol when it is being trued up. When protuberance 22 is approximately7 inch in diameter, a taper to a 4; inch diameter root within inch oflength is sufliciently shallow to maintain control.

To illustrate that protuberance 22 may be formed in an almost infinitevariety of shapes, a number of variations are shown in Figs. 6-10. Figs.6, 7 and 8 show protuberances formed adjacent the ends 36a, 36b and 36crespectively of devices 10a, 10b and 100. End 36:: in Fig. 6 ishemispherical for example. End 3612 in Fig. 7 is formed of a largerportion of a sphere, and end 360 in Fig. 8 is abruptly cut oil atcircumferential protuberance 220.

Fig. 9 shows a protuberance 22d which is formed by a ring 22a formed orpressed upon a straight-sided smaller diameter shank section 27d.

awith'out further;adjustment or "tightening.

V Inc'Fig. 10,protuberance22e is formed by a ring-shaped irotatin'giholder'such as a four jawed chuck 14,

' Theicentering procedure isex tremely simple. Device 110zis *securedwithin rotating chuck or holder I4 u'nder V 10 diameter "section tapersfrom armor-diameter oft-rapordinary' pressure, and micro drill 12 is'likewise'secured withimfchucklfl. The drill' is then rotated and light-pressure 2applied, for example, by a pencil point-42 rto'true =upthe'drill. The hole is then-drilled whatissclaimed isz r 5 7 t1; devicefor mounting 'and centering a micro drill -inia' rotatingholdercompris'ing an exposed. shankga chuck .sdisposedmtioneiend ofisaidshank for holdingtheblunt vendnof said'imicr'odrill, an exposedcircumferential prot i. .tuberanceadjacenttthe otherendof saidshankwhich is fi-iins'ertable :into said rotating holder, said 'protiiberance-providing suflicient area"of'contact between said zshank rand}saidrotating holder todrive said micro Tdrill under rllfl ald iall d'SQid PIOIHbEI'aHC-E PIOjQCtiDg outwardly from said shank a distancesufiicient to permit'said deviceto ,pivot gabout it within"said rotatingholder upon the ap- ..p1ication:of.alateral:force to the lower'portio'no'f-said fideviceito' zcentersaid i drill. V a

r. Adevice'as-set forth'in-vclaim 1 wherein said pro- ;iuberanceis;cmprised of:a circumferential bulge near theaend.ofcsaid shank,isaidshank tapering-down adjacent :said bulgef'to ".a :smaller diameterroot, and said root 7 -fii3fl16tlfiS large venou'ghito' prevent -the endor saidas'hank I rfrom .passing through said rotatidgholder when saiddeviceis pivoted;

/ ';-=3'.;A deviceiassetiforth in claim l'wherein saidshank is comprised'ofiadarger diameter section for receiving f: and mounting said microidrill chuck'and a' smaller diam 'etersectionforfmountingsaid devicewithins'aidrotating tzholder.

4.1A;device-as*set 'forth in claim 3 wherein said chuck includes a jawedassembly andaclosing ring said larger 1 diameter =sectionincli1desa:central-bore for receiving 5 is comprised of a collet closing ring.

said jawed assembly and its .outer surface is threaded for mounting saidclosingring. j

t 5. A device as set forth in claim 4 wherein said jawed assembly iscomprised of a collet, and said closing ring 6. A device as set forth inclaim 3 wherein thediameter of said protuberance :is ;greater than thediameter of the largest micro drill to beheld in said device.

' 7. A device as set forth-in claim Swhereinsaid smaller mately inch.

9. A device asset forth in claim 6 wherein the distance betweuen saidprotuberance and the chuck end of said device is approximately 1 /2inchesand more to per- 'mit' the'tipof saiddrill' to be centered while acondition or eccentricity=exists atsaid protuberance.

- 10. A device as set fortlrin claim '3 wherein said protuberance isdisposed approximately at the centenof-said smaller diameter section.

7 '11. -A device'as set'forth in-claim' l wherein sai'dprdtuberance iscomprised of acurved'bulge,

12. A;device as set for'thin claiml-wherein said protuberance isdisposed at the end of said shank.

13. A device as set forth-in claim 1 wherein said protuberance iscontinuous about the periphery of said shank. 1

- 514. A device as set forth in claim l 'whereimsaid protiiberanee isinterrupted by-s'lots spacedabodt-itsiieriphery. i

1 5-. A device 'as set forth in-claim 'l whereiirthe plane including thehigh point-of said protuberance is substantially perpendicular to thelongitudinal axisjof' said V shank.

1 References Cited-inthe file of patent 40 UNITED STATES PATENTS 7Hoffsommer May 23, 1950 -Wi1liams Dee-'4, 1951 Olson Apr. 13, 71954

